#include<iostream>
#include<cstdio>
#include<math.h>
using namespace std;
int main(){
	//freopen("in.txt","r",stdin);
	//freopen("ans.txt","w",stdout);
	int n;
	double sum=0,count=0,t=0,ans,m;
	cin>>n;
	if(n==3){
		t=4.3;
	}
	else if(n==10){
		t=2.26;
	}
	else if(n==20){
		t=2.09;
	}
	else{
		t=2;
	}
	double x[n];
	for(int i=0;i<n;i++){
		cin>>x[i];
		sum+=x[i];
	}
	sum/=n;
	for(int i=0;i<n;i++){
		count+=((x[i]-sum)*(x[i]-sum));
	}
	m=n*(n-1);
	ans=t*sqrt(count/m);
	printf("%.4lf",ans);
	//fclose(stdin);
	//fclose(stdout);
}
